Shrinkproofing and feltproofing with acid bromate wetting agent solution



I S-3B9 mas SEQRCH Rm Oct. 8, 1963 3,106,440

M. LEWIN SHRINKPROOFING AND FELTPROOFING WITH ACID BROMATE WETTING AGENT SOLUTION Filed April 17, 1961 Inventor mamc'xem nswm m ww Attorneys United States Patent Office 3,106,440 Patented Oct. 8, 1963 SHRINKPROOFING AND FELTPROOFING WITH ACID BROMATE WETTHW G AGENT SOLUTION Menachem Lewin, Jerusalem, Israel, assignor of one-half to the Government of Israel on behalf of the State of Israel, Jerusalem, Israel Filed Apr. 17, 1961, Ser. No. 103,342 Claims priority, application Great Britain Apr. 28, 1960 12 Claims. (Cl. 8-128) This invention provides a process for making wool shrinkproof and feltproof, which terms are used in the art synonymously with resistance to washing shrinkage and to fulling shrinkage, respectively.

The term wool used in connection with the present invention includes wool fibres, such as tops or loose fibres; yarns; textile goods made from wool fibres or yarns such as woven and knitted fabrics, blankets, felt and the like; blends of wool with natural, artificial or synthetic fibres such as, for example, cotton, rayon, polyamide, polyester and polyacryl fibres, in the form of yarns or fabrics.

More particularly, the present invention relates to those processes for shrinkproofing and feltproofing wool in which a bromate is used as an active agent, as contrasted to other known processes, mainly those which use free or nascent halogen.

A known bromate process for rendering wool shrinkproof and feltproof is described in British patent specification No. 798,236. This is a development of an earlier process, described in British Patent specification No. 614,271, which achieved shrinkproofing but not feltproofing of the Wool. Both processes are performed in a single stage in which the wool is immersed in a bath consisting of an aqueous solution containing a watersoluble bromate and hydrogen chloride. The process according to specification No. 798,236 is distinguished from that according to specification No. 614,271 by the bromate and hydrogen chloride concentrations of the bath and by the fact that in the later process the bath also contains initially a sizable proportion of the chloride of an alkali or alkaline-earth metal, which is initially absent in the earlier process, though it forms in the bath in the course of the treatment by the reaction of the bromate with HCl.

Of these two known processes, the later is superior to the earlier one, but even so it has still some drawbacks, mainly the required long time of dwell of the wool in the bath, about one hour to three hours, which makes it impossible to conduct the process in a continuous manner, and the required comparatively large liquor-to-fibre ratio.

The invention has the object to provide a process for shrinkproofing and felt-proofing wool by a treatment with an aqueous bromate-containing liquor, wherein the treatment of the wool is terminated in a much shorter time, being of the order of seconds, and appreciably lower liquor-to-wool ratios are required than hitherto.

According to the invention the wool is impregnated with an aqueous bromate liquor containing a wetting agent, freed from excess impregnating liquor by squeezing, and successively treated with an acid at a temperature of not below 25 C. and with the aqueous solution of a reducing agent, and subsequently with ammonia or any other suitable alkaline agent such as, for example, an aqueous alkali metal bicarbonate or carbonate.

For the sake of brevity, the stages of treatment with acid, with a reducing agent and with ammonia will be referred to hereinafter, respectively, as development, reduction and neutralization.

The bromate liquor may, if desired, contain the chloride of an alkali or alkaline-earth metal, e.g. in a pro portion of from 1 g. per litre up to saturation. .Though the use of such a chloride is not indispensable, it is desirable since it accelerates the development and makes the wool even less liable to be damaged by the development.

The bromate used may be potassium bromate, e.g. in a concentration between 20 and g. per litre, or any other suitable water-soluble bromate in an equivalent concentration.

For producing a complete shrinkproofing eflect without damaging the wool, the amount of bromate available for the reaction in the development stage should be not below 1.5% and preferably not above 2.6%, calculated as KBrO on the oven-dry weight of the wool. The presence of a wetting agent in the impregnating liquor is required for a thorough wetting of the wool, which in turn is necessary in order to ensure homogeneity of the development in all parts of the mass of fibres. The liquor pick-up of the wool in the impregnation stage, as adjusted by the subsequent squeezing operation, should be from about 30 to about 130%, calculated on the air-dry wool; it will be varied in accordance with the bromate concentration of the liquor.

For the development, inorganic acids are preferred in practice because of their lower costs, but from a technical point of view, the use of organic acids is not excluded. Suitable acids are, for example, hydrochloric, sulphuric and pcrchloric acids.

By one embodiment of the invention the development is effected with an aqueous acid, preferably of a concentration not below 0.3 N. In this case the development may be performed by immersion of the wool in the acid or by spraying the acid onto the wool.

By another embodiment of the invention, applicable to volatile acids, the development is effected by contacting the impregnated Wool with the gaseous or vaporous acid, eg with gaseous HCl.

The development preferably takes place at a temperature between 40 and 100 C. Where the wool is immersed in an acid bath, the bath will be kept at the desired temperature. In the case of spraying or of treatment with a gaseous or vaporous acid, the wool itself may be warmed, eg by irradiation by means of infrared lamps.

There exists an interdependence between several factors each of which is variable within wide limits, namely: the strength of the acid; the concentration of the acid; the temperature maintained at the development stage; the time of the development; absence or presence of chlorides in the impregnation bath or the development bath, and in the case of their presence, their concentration in that bath. In a general way it can be said that the hgher the concentration of chloride in the impregnating liquid, the lower may be the temperature and acid concentration and the shorter the time of treatment in the development stage. Under equal conditions of chloride concentration (or absence of chloride), the higher the concentration of the acid and/ or the temperature in the development stage, the lower may be the duration of this stage. For example, with a 0.3 N acid, the development will have to be carried out at elevated temperatures, eg at -100 C. With a 1.5 N acid, the temperature maintained during the development may be as low as 40-35 C.; in both cases the development time may be of the order of seconds.

The reduction stage serves for the removal from the wool of any oxidants remaining in the wool after the development. It is preferably performed at a temperature between 30 and 50 C. Suitable reducing agents are, for example, water-soluble sulphites, bisulphites, thiosulphaites and hydrosulphites, particularly the alkali metal salts. If a sulphite, bisulphite or hydrosulphite is used, the wool undergoes bleaching in the reduction stage, the brightness of the wool increasing with the concentration of the reducing agent and the temperature at which the reduction is performed. It has been found that with sodium hydrosulphite as a reducing agent, a brightness of above 70% (measured with the Photovolt Brightness Tester with magnesium carbonate as standard 100% brightness) can be obtained, which almost corre sponds to full bleaching of the wool. For practical purposes it is convenient to use relatively dilute solutions of the reducing agent, e.g. of the order of 0.1 to 1%.

In the neutralization stage the wool is immersed in dilute aqueous ammonia, dilute aqueous alkali metal, e.g. sodium bicarbonate or carbonate, or the like.

No exact theoretical explanation of the action of the bromate on the wool can be given, nor of the empirical fact that the treatment of the wool in stages in accordance with the present invention is superior to the singlestage earlier processes referred to above. Presumably, the bromate of the liquid with which the fibres are impregnated is converted by the development into free bromic acid which rapidly reacts in situ with the fibres. It can be said, however, that the process according to the invention does not consist in the action of free halogen either in the molecular form or in statu nascendi on the wool. This is proved by the fact that the process can be performed by impregnating the wool with potassium bromate (or another suitable bromate) in the absence of a halide, with perchloric acid being used in the development stage.

Perchloric acid is very stable and does not react with wool or with the bromate ion to form free halogen.

In contrast to what happens in the earlier processes referred to above, it has been found that in the process according to the invention the amount of the bromate anion retrievably sorbed on the wool is negligible and cannot be determined analytically. The retrievably sorbed bromate contained in the wool treated by the earlier processes is not reduced by the wool and can be retrieved from it by prolonged washing in water. Such sorbed bromate is apt, in storage or on heating, slowly to attack and weaken the wool. In the process according to the present invention, all the bromate taken up by the wool disappears in the development stage and no bromate can thereafter be detected on the wool. More over, since the time of contact of the wool with the acid is very short, only a small proportion of acid anion is sorbed on the wool. Hence, the neutralization of the wool is easy and requires only small amounts of ammonia and a short time. This ensures a homogeneous pH of the wool and facilitates its dyeing.

During the short development stage some of the bromic acid is apt to diffuse onto the acid bath before having reacted with the wool. This diffused bromic acid will react with the bromide produced by the reduction of the main part of bromic acid and by this secondary reaction a very small quantity of elementary bromine may be produced. Although this elementary bromine will not substantially influence the treatment it is possible to eliminate it, if desired, either by a stream of air bubbled through the development bath by which the bromine is carried oil, or by recirculation of the development bath through a column in countercurrent with a. stream of air which removes the bromine while the purified acid is returned to the development bath.

Wool treated by the process according to the present invention does not change its handle and its microscopic features (i.e. the scales are not damaged). It withstands the most severe alkaline as well as acid milling tests without shrinking or felting. The colour of the undyed wool remains unchanged or undergoes partial or almost full bleaching, according to the selected conditions of the reduction stage, its alkali solubility increases only slightly. There is a slight increase of the strength properties of the treated woo1, especially in the dry state of the latter.

It has surprisingly been found that wool treated by the process according to the present invention has a considerably increased resistance to abrasion, as compared to the untreated wool. The Wool has an increased abrasion resistance in both the dry and the wet state, and it keeps it even after a considerable number of washings.

The wool treated according to the present invention is homogeneously modified and can safely be dyed with a large range of dyestuffs.

The handle of the wool can be modified by an aftertreatment of the wool with an aqueous soap solution at 30 to 50 C. after the neutralization stage.

The soap solutions may be used in concentrations of 1 to 10 grams per litre; the higher the concentration of the soap, the softer is the handle of the wool. This possibility of modifying the handle is an advantage as the handle of the wool is an important property which, although it cannot be measured precisely, greatly affects the marketability of the wool. Sometimes higher softness or a finer handle is desired in the trade, and sometimes a harsher wool is preferred, similar to original not shrinkproofed wool.

The invention is illustrated by the following examples to which it is not limited. Indications of percentages are by weight of air-dry wool.

EXAMPLE 1 1 kg. of woven blanket fabric made of pure wool was impregnated in 10 litres of a solution containing per litre 29.8 g. of potassium bromate, 117 g. of sodium chloride and 5 'g. of a non-ionic wetting agent (known under the trademark Ultravon JU). The impregnation was carried out on a Foulard-type padding mangle at 40 C. The impregnated wool was squeezed between rollers so adjusted that after the removal of excess solution the pickup of the solution on the fabric was 86.0%, calculated on the air-dry weight of the fabric. The impregnated fabric was dried in an air stream in a drying oven at 105 C. and thereafter immersed for 25 seconds at 50 C. in 20 litres of an aqueous acid solution containing 17 g. (about 0.5 N) of I-ICl per litre. The fabric was then squeezed between rollers and rinsed in water. The spent rinsing water contained no potassium bromate. The fabric was then rinsed at 30 C. in 10 litres of an aqueous solution containing 0.3 g. per litre of sodium bisulphite, then squeezed between rollers, and rinsed at 30 C. in 10 litres of aqueous ammonia containing 1 'g. of NH per litre, squeezed between rollers and rinsed in 10 litres of an aqueous solution containing 2 g. per litre of soap, squeezed between rollers rinsed with water and dried.

Milling-shrinkage tests were made in accordance with the following testing procedure:

Before the actual milling-test the relaxation shrinkage of the fabric or knitwear is determined.

(1) Determination of the Relaxation Shrinkage The sample of the material 12 x 12 cm. is marked with indelible ink or paint at distances of 10 cm. lengthwise and Widewise.

The marked sample is put at a liquor-ratio of 1:20 in water containing 0.5 g. of wetting agent preferably DDBS (dodecylbenzene sulphonate) at a temperature of 37-40 C. and left at these conditions for at least 2 hours (preferably overnight) without any movement.

The measurements are carried out to the nearest millimeter under distilled water at 37 C. The difference in the measures of the material before and after the relaxation constitute the relaxation shrinkage.

(2) Milling-T est: Alkaline The marked samples of the material (usually 2-3) are put in a 1% aqueous soap solution at 50 C. and vigorously milled for 10 minutes by hand. The samples are rinsed in water and measured under distilled water at ca. 37 C.

The differences in the dimensions of the warp, weft and area between of the sample after the relaxation test and after the milling test give the milling shrinkage in percents of the relaxed sample.

(3) Milling-T est: Acid This test is carried out in the same way as the alkaline milling test, but instead of a soap solution, a 1% aqueous acetic acid at 37 C. is used.

This test is also carried out on a relaxed sample.

In this example, the alkaline milling shrinkage of the fabric, treated as described above, in the warp direction was 1%, in the weft direction 0.0%, and the area shrink age was 1%.

The alkaline milling shrinkage of the untreated fabric in the warp direction was 11.2%, in the weft direction 12%, and the area shrinkage was 21.8%.

The handle of the treated fabric was undistinguisha'ble from that of the untreated wool.

EXAMPLE 2 1 kg. of knitted fabric made of pure wool was immersed at 60 C. in a Foulard-type padding mangle in litres of an aqueous solution containing per litre: 44 g. of sodium bromate, 160 g. of potassium chloride and g. of Ultravon JU. After the impregnation the fabric was squeezed between the rollers of the mangle so that the pick-up of the solution on the fabric was 51%, calculated on the air-dry weight of the fabric. The impregnated fabric was immersed for 3 seconds at 70 C. in litres of an aqueous hydrochloric acid solution containing 20 'g. of HCl per litre, squeezed between rollers and rinsed in water. The spent rinsing water contained no bromate. The fabric was further processed as described in Example 1, except that instead of sodium bisulphite, 0.5 g./litre of sodium sulphite was used for the reduction stage, and no after-treatment with soap was effected. The alkaline milling shrinkage of the treated fabric was 0.5% in the length direction, 1% in the width drection, and the area shrinkage was 1.5%. The alkaline milling shrinkage of the untreated fabric was 27% in the length direction, 18% in the width direction, and the area shrinkage was 42%.

The acid milling shrinkages of the treated fabric were correspondingly 1.0%, 0.7%, 1.7% and of the untreated fabric 25.5%, 13% and 35.9%.

EXAMPLE 3 The process described in Example 2 was carried out in a continuous manner by means of an experimental plant diagrammatically illustrated in the accompanying drawing. This plant comprised a two-bowl padding mangle including an impregnating vat 1, and an open-width washing machine divided into compartments 2, 3, 4, 5 which served, respectively, as development, reduction, neutralization and rinsing vessels. A pair of mangle rollers 6 was interposed between vat 1 and vessel 2, and pairs of squeezing rollers 7, 8, 9, =10 at the outlet ends of vessels 2, 3, 4, 5, respectively. An appropriate number of guide rollers 11 was disposed in conjunction with the vat 1 and each of the vessels 2, 3, 4, 5, for keeping the web of fabric 12 submerged in each bath and guiding it along its path through the plant.

The impregnating bath in vat 1 was an aqueous solution containing per litre: 44 g. of sodium bromate, 160 g. of potassium chloride and 10 g. of wetting agent Ultravon JU. It was kept at 60 C., and its level was kept substantially constant by the addition of make-up liquor.

The squeezing pressure of rollers 6 was so adjusted that the liquor pick-up of the fabric (the same knitted pure-wool fabric as used in Example 2) was 50% of the air-dry weight of the fabric.

The development bath in vessel 2 consisted of aqueous hydrochloric acid (20 g. of HCl per litre) at 70 C. The time of passage of the fabric through this bath was adjusted to 3-4 seconds.

The reduction bath in vessel 3 consisted of an aqueous sodium sulphite solution (0.5 g. per litre) at 3050 C.

The neutralization bath in vessel 4 was dilute aqueous ammonia (1 ml. of concentrated aqueous ammonia per litre) at 30-50 C.

The rinsing bath in vessel 5 was tap water.

The baths in vessels 3, 4 and 5 were continuously drained and refilled so that their respective volumes and compositions remained substantially constant.

The fabric continuously leaving the vessel 5 had substantially the same properties as that obtained by the process described in Example 2.

EXAMPLE 4 1 kg. of slubbing (top silver) of pure wool was impregnated in 5 litres of a solution of a similar composition as described in Example 2. After squeezing, the pick-up of the solution on the slubbing was 50%. The development was done by immersion of the impregnated slubbing in 20 litres of 1 N-aqueous sulphuric acid at C. for 10 seconds, followed by rinsing in water. The spent rinsing water contained no bromate. The slubbing was further processed as described in Example 2. It did not felt in the alkaline and acid milling tests and the individual fibres could be easily separated.

The colour of the treated slubbing was visibly brighter than of the untreated one.

EXAMPLE 5 1 kg. of 32/2 yarn made of pure wool was impregnated in 5 litres of an aqueous solution containing per litre: 49 g. of potassium bromate and 20 g. DDBS (dode-cylbenzene sulphonate).

The impregnation was done in a Foulard-type padding mangle at 40 C.; the pick-up of the solution on the yarns was 52%, calculated on the air-dry weight of the wool. 'Ihe impregnated yarn was immersed for 10 seconds in 20 litres of a 1 N-aqueous perchloric acid at 80 C. and thereafter rinsed in water and further processed as described in Example 2 except that instead of sodium sulphite, hydrosulphite was used.

The alkali solubility determined by the ASTM (American Society of Testing Materials) method, Standard No. D 1283-53 T on the yarn before the ammonia neutralization stage was 16.3%.

The yarns did not felt in the alkaline and acid milling tests, and the individual yarns could easily be separated. The colour of the treated yarn was visibly brighter than that of the untreated yarn.

In the table below the physical properties of the treated yarn are compared to those of the untreated yarn. Each of the tensile strength figures given in the table is an average of 32 measurements on the LP. 2 Scott tester. Each of the abrasion resistance figures is an average of 39 measurements on a yarn abrasion tester as described in US. patent specification No. 2,820,362.

TABLE Physical Properties of Untreated and Treated Yarn Abrasion resistance, number of rubs Tensile strength, g.

dry wet untreated treated EXAMPLE 6 at 40 C. After the squeezing the pick-up of the solution on the fabric was 50%, calculated on the air-dry weight of the fabric. The impregnated fabric was sprayed with 3 litres of 1 N-aqueous hydrochloric acid at 60 C., rinsed in water and further processed as described in Example 2. The alkaline milling shrinkage of the treated fabric was 0.0 in the length direction, 1.2% in the width direction, and the area shrinkage was 1.2%.

I claim:

1. A process for making wool 'shrinkproof and feltproof, comprising treating the wool with an aqueous solution of a bromate and a wetting agent to impregnate the wool with bromate, removing excess solution from the wool to provide wool impregnated with about 30 to 130 percent by weight of bromate solution per weight of airdry wool, developing the bromate by treating the impregnated wool with acid at a temperature of at least about 25 C., removing oxidants from the wool by means of a reducing agent, and neutralizing the wool.

2. A process according to claim 1, in which the acid used in developing the bromate is at a temperature of about 40 to 100 C. and at a concentration of at least about 0.3 N.

3. A process according to claim 1, wherein the reducing agent used in the reducing step is a dilute aqueous solution of a salt selected from the group consisting of water-soluble sulfites, bisulfites, thiosulfates and hydrosulfites.

4. A process according to claim 1, in which the aqueous bromate solution contains the chloride of at least one metal selected from the group consisting of alkali metals and alkaline earth metals in a concentration of from 1 g. per liter to saturation.

5. A process for making wool shr-inkproof and feltproof which comprises treating wool with an aqueous so lution containing a wetting agent and a bromate selected from the group consisting of alkali metal and alkaline earth metal bromates at a concentration of from 20 to 80 grams calculated as KBrO per liter, so as to impregnate said wool with bromate, removing excess impregnating liquor by squeezing the wool, and thereafter developing the bromate impregnated wool by treatment with an aqueous acid at a concentration of at least 0.3 N at a temperature between 40 and 100 C., removing oxidants from the wool by means of a reducing agent, and neutralizing the wool by means of an alkaline neutralizing agent.

7 6. The process of claim 5 wherein sufiicient excess impregnating liquor is removed from the impregnated wool so that a proportion of 1.5 to 2.6 percent, calculated as KBrO on the weight of wool in the oven dry state, is available for reaction in the development stage.

7. The process of claim 5 wherein an inorganic acid selected from the group consisting of hydrochloric acid, sulfuric acid and perchloric acid is used in the development stage.

8. A process according to claim 5, wherein the neutralization agent used in the neutralization step is selected from the group consisting of aqueous solutions of ammonia, alkali metal bicarbonates and alkali metal carbonates.

9. A process according to claim 1, in which the neutralized wool is treated with an aqueous soap solution.

10. A process for making wool shrinkproof and feltproof, comprising treating the wool with an aqueous solution of a bromate and a wetting agent to impregnate the Wool with bromate, removing excess solution from the wool to provide wool impregnated with about 1.5 to 2.6 percent bromate calculated as KBrO per weight of ovendry wool, developing the bromate by treating the impregnated wool with acid at a temperature of at least about 25 C., removing oxidants from the wool by means of a reducing agent, and neutralizing the wool.

11. A process according to claim 5, in which excess bromate solution is removed from the wool by squeezing the wool.

12. A process according to claim 5, in which the aqueous bromate solution contains the chloride of at least one metal selected from the group consisting of alkali metals and alkaline earth metals in a concentration of from 1 g. per liter to saturation.

References Cited in the file of this patent UNITED STATES PATENTS 2,714,051 Barnes July 26, 1955 2,923,596 Levin Feb. 2, 1960 FOREIGN PATENTS 551,310 Great Britain Feb. 17, 1943 723,561 Great Britain Feb. 9, 1955 

1. A PROCESS FOR MAKING WOOL SHRINKPROOF AND FELTPROOF, COMPRISING TREATING THE WOOL WITH AN AQUEOUS SOLUTION OF A BROMATE AND A WETTING AGENT TO IMPREGNATE THE WOOL WITH BROMATE, REMOVING EXCESS SOLUTION FROM THE WOOL TO PROVIDE WOOL IMPREGNATED WITH ABOUT 30 TO 130 PERCENT BY WEIGHT OF BROMATE SOLUTION PER WEIGHT OF AIRDRY WOOL, DEVELOPING THE BROMATE BY TREATING THE IMPREGNATED WOOL WITH ACID AT A TEMPERATURE OF AT LEAST ABOUT 25*C., REMOVING OXIDANTS FROM THE WOOL BY MEANS OF A REDUCING AGENT, AND NEUTRALIZING THE WOOL. 